Edward Snowden, a 29-year-old former CIA employee and National Security Agency contractor, identified himself this weekend as the source of several documents describing the broad scope of the U.S. government’s surveillance activities. Here is a summary of what Snowden revealed.

One of the documents was a secret court order regarding information about telephone calls:

The order appears to require a Verizon subsidiary to provide the NSA with daily information on all telephone calls by its customers within the United States and from foreign locations into the United States. ¶ The order, which was signed by a judge from the secret court that oversees domestic surveillance, was first reported on the Web site of the Guardian newspaper. The Web site reproduced a copy of the order, which two former U.S. officials told The Washington Post appears to be authentic. ¶ A senior Obama administration official said Thursday that the purported order “does not allow the government to listen in on anyone’s telephone calls” but relates only to “metadata, such as a telephone number or the length of a call.” The official said such information “has been a critical tool in protecting the nation from terrorist threats to the United States.”

The National Security Agency and the FBI are tapping directly into the central servers of nine leading U.S. Internet companies, extracting audio and video chats, photographs, e-mails, documents, and connection logs that enable analysts to track foreign targets. . .¶ The program, code-named PRISM, has not been made public until now. It may be the first of its kind. The NSA prides itself on stealing secrets and breaking codes, and it is accustomed to corporate partnerships that help it divert data traffic or sidestep barriers. But there has never been a Google or Facebook before, and it is unlikely that there are richer troves of valuable intelligence than the ones in Silicon Valley.

Government officials and representatives of technology companies have argued that these modes of surveillance are legal and appropriately supervised (see articles here and here). Here is an explanation of the NSA’s function as “the government’s eavesdropper-in-chief”:

Charged primarily with electronic spying around the globe, the NSA collects billions of pieces of intelligence from foreign phone calls, e-mail and other communications. But in the past two days, the focus has shifted to its role in compiling massive amounts of the same information on millions of ordinary Americans. . .¶ The agency is so secretive that estimates of the number of employees range from the official figure of about 35,000 to as high as 55,000. In addition to its main campus behind the walls of Fort Meade, the NSA will operate a new surveillance center in the Utah desert. The million-square-foot building will cost about $2 billion when it’s finished, perhaps as early as the fall. The center is designed to capture all forms of communication for the nation’s intelligence agencies, ranging from e-mail and cellphone calls to Internet searches and personal data.

Read an account of an interview with Snowden, the man who claims responsibility for the disclosures, here and a profile of him here. He fled the United States to Hong Kong, but his current location is not known, and China is likely to extradite him if he remains there and the United States seeks to charge him. Reporter Barton Gellman wrote this account of his relationship with Snowden:

He called me BRASSBANNER, a code name in the double-barreled style of the National Security Agency, where he worked in the signals intelligence directorate. Verax was the name he chose for himself, “truth teller” in Latin . . .¶ Edward Joseph Snowden, 29, knew full well the risks he had undertaken and the awesome powers that would soon be arrayed to hunt for him. Pseudonyms were the least of his precautions as we corresponded from afar. Snowden was spilling some of the most sensitive secrets of a surveillance apparatus he had grown to detest. By late last month, he believed he was already “on the X” — exposure imminent. ¶ “I understand that I will be made to suffer for my actions, and that the return of this information to the public marks my end,” he wrote in early May, before we had our first direct contact. He warned that even journalists who pursued his story were at risk until they published.